Dominant contributions to the apparent activation energy in two-dimensional submonolayer growth: comparison between Cu/Ni(111) and Ni/Cu(111)

For surface-mediated processes in general, such as epitaxial growth and heterogeneous catalysis, a constant slope in the Arrhenius diagram of the rate of interest, R, against inverse temperature, log R vs 1/T, is traditionally interpreted as the existence of a bottleneck elementary reaction (or rate...

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Bibliographic Details
Published in:Journal of physics. Condensed matter 2020-10, Vol.32 (44), p.445002
Main Authors: Alberdi-Rodriguez, Joseba, Acharya, Shree Ram, Rahman, Talat S, Arnau, Andres, Gosálvez, Miguel A
Format: Article
Language:English
Subjects:
apparent activation energy
epitaxial growth
island diffusion
kinetic Monte Carlo
surface morphology
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Summary:For surface-mediated processes in general, such as epitaxial growth and heterogeneous catalysis, a constant slope in the Arrhenius diagram of the rate of interest, R, against inverse temperature, log R vs 1/T, is traditionally interpreted as the existence of a bottleneck elementary reaction (or rate-determining step), whereby the constant slope (or apparent activation energy, EappR) reflects the value of the energy barrier for that elementary reaction. In this study, we express EappR as a weighted average, where every term contains the traditional energy barrier for the corresponding elementary reaction plus an additional configurational term, while identifying each weight as the probability of executing the corresponding elementary reaction. Accordingly, the change in the leading (most probable) elementary reaction with the experimental conditions (e.g. temperature) is automatically captured and it is shown that a constant value of EappR is possible even if control shifts from one elementary reaction to another. To aid the presentation, we consider kinetic Monte Carlo simulations of submonolayer growth of Cu on Ni(111) and Ni on Cu(111) at constant deposition flux, including a large variety of single-atom, multi-atom and complete-island diffusion events. In addition to analysing the dominant contributions to the diffusion constant of the complete adparticle system (or tracer diffusivity) and its apparent activation energy as a function of both coverage and temperature for the two heteroepitaxial systems, their surface morphologies and island densities are also compared.
ISSN:0953-8984
1361-648X
DOI:10.1088/1361-648X/ab9b50